Method for transmitting control data between a base station and a mobile station

ABSTRACT

Apparatuses and methods for transmitting control data on a physical channel between a mobile radio device and a base station in a cellular network. In particular, in a mobile radio network according to the UMTS standard (UMTS=Universal Mobile Telecommunication System) a packet-oriented data transmission between the mobile radio device and the base station is controlled using control data, wherein the control data includes a packet number for identifying a data packet.

FIELD OF TECHNOLOGY

The present disclosure generally relates to transmitting control data ona physical channel between a mobile radio device and a base station in acellular network

BACKGROUND

In cellular mobile radio systems a communication connection isestablished between a mobile radio device, generally also referred to asa terminal, a mobile terminal or user equipment (UE), and the mobileradio network via a so-called base station. The base station servesmobile radio users in a specific area a so-called cell via one or moreradio channels. Such a base station also referred to as node B in theUMTS standard provides the actual radio interface between the mobileradio network and the mobile terminal. It deals with the radio operationwith the different mobile users within their cell and monitors thephysical radio connections. It also transmits network and statusmessages to the terminals. A distinction is made between two connectiondirections in mobile radio. The downlink DL describes the direction fromthe base station to the terminal, the uplink UL the direction from theterminal to the base station.

Generally a number of different transmission channels exist in eachdirection. There are therefore so-called dedicated channels, forexample, for the specific transmission of information from or for aspecific terminal. There are also so-called common channels, which serveto transmit information intended for a number or even all of theterminals from the base station. Similarly there are common channels inthe backward direction, which the different terminals share, forexample, for the transmission of short messages or control data to thebase station, each terminal only using the channel for a short time. Thedifferent channels are thereby generally multi-layer in structure. Thebase is a so-called physical channel, referred to as layer 1 for examplein the UMTS standard.

To transmit the different data elements, different logical channels areimplemented on different higher layers on top of the physical channel,i.e., the lowest layer. Data is thereby generally transmitted on thephysical channel in a packet-oriented manner, i.e., the data to betransmitted is divided into individual packets, which are senttemporally one after the other. Control data is also transmitted inpacket form generally with a temporal offset parallel to the useful datato be transmitted. This is required on the recipient side in order toidentify the packets and re-assemble them correctly. The control datacan thereby include a packet number for example, which serves toidentify a data packet.

A typical example of such a physical channel, on which such atransmission method is used, is the so-called HSDPA (High Speed DownlinkPackage Access) channel. This is a downlink channel according to themost recent UMTS standard. The transmission method used there is a fast,so-called HARQ

Method (HARQ=Hybrid Automatic Repeat Request). An ARQ method (AutomaticRepeat Request) is an error protection method, with which the blocks tobe transmitted are continuously numbered and provided with a block checksequence, which the recipient uses to decide whether a transmissionerror has occurred. Correct blocks are acknowledged by the recipientusing a so-called ACK signal. The recipient responds to an incorrectblock either with a negative acknowledgement, a so-called NACK signal,or the block is ignored, whereupon the sender repeats the transmissionafter a predefined period of time. The sender only sends a new packet onthe same channel, when the immediately preceding block has beenpositively acknowledged by the recipient (so-called stop and waitmethod).

The term hybrid means that parity bits (check bits) are also transmittedfor error protection purposes. A multi-channel stop and wait protocol(so-called n-channel stop and wait) is used on the HSDPA channel.Temporal distribution is thereby used on the physical channel toimplement a number of time channels, to which different transmissiontime intervals are assigned, each corresponding to a block length. Thisallows further blocks to be sent in the other time channels whilewaiting for the acknowledgement for a transmitted block in one timechannel. The channel number of the respective time channel must be sentspecifically as a control parameter to the recipient from the sender forexample. Whether a transmitted block is a new packet or are-transmission of the last packet can be seen from the packet numberreferred to above for identifying the data packet.

Only a limited number of packet numbers are thereby available for eachtime channel and these are always used in a cyclically alternatingmanner. In other words, after the last packet number has been used, thenext new data packet is given the first number again, etc. In the caseof the HSDPA channel, this packet number is referred to as the so-callednew data indicator NDI. In the case of the HSDPA, only 1 bit is madeavailable for this and it changes value with each new packet.

The different control parameters required for control purposes, e.g.,the channel number and packet number, first have to be coded in thecontext of a source-coding before transmission. In the case of theHSDPA, the channel number is source-coded into 3 bits. The packet numberis thereby source-coded separately into a 1-bit packet number. Theinformation data thus generated is then channel-coded. In a so-calledrate matching method, this data is then reduced such that it can betransmitted within a defined transmission time interval of a timechannel, which is two milliseconds in the case of the HSDPA.

However the use of this HSDPA method for uplink signaling from theindividual terminals to the base station is relatively unfavorable. Aso-called SHO method (SHO=soft handover) method is frequently used onthe uplink channels. With this method, a radio connection issimultaneously maintained between the terminal and the network in aparallel manner via a number of base stations, such that a terminalmoving within the network can be handed over in a smooth manner betweenthe individual base stations. In the SHO method, the power regulation ofthe terminal is controlled such that decoding can take placesuccessfully on one of the connections at least. This means, however,that often only the base station with the best channel conditions candecode the associated control data. For other base stations using theSHO method, a number of packets with the associated control data may notbe comprehensible. Also a soft-combining method is generally used toimprove transmission quality with the current standards. Differenttransmissions of a packet are thereby superimposed before decoding,i.e., the first transmission is used first and if this cannot bedecoded, the re-transmission is superimposed with the firsttransmission, thereby increasing the signal energy of the packet. Withthis per se advantageous combination of soft handover and soft combiningthe problem arises that a 1-bit packet number is not adequate to preventincorrect superimposition of different packets.

This is illustrated using the following example: Where there are threesuccessive packets, if only one 1-bit packet number is used, these aregiven the packet number 0,1,0. If one of the base stations using the SHOmethod does not receive the middle packet with the packet number 1, butanother base station does, the receiving base station will acknowledgethe packet. The terminal then sends the third packet again with thenumber 0. The base station which could not decode the middle packet thenassumes that the third packet is a re-transmission of the first, sincethe packet number has not changed between two decoded packets. This basestation will, therefore, try to decode the packet with the transmissionsof both packets superimposed. As the packets do not, however,correspond, this decoding attempt will inevitably fail. Such frequentlyoccurring events have a negative effect on system performance.

One possible way of avoiding this problem would be to use an n-bitpacket number where n>1. In this instance, there is only a risk ofconfusing a new packet and a re-transmission of the last packet, if therecipient in question has in the meantime been unable to decode any ofthe transmissions of 2n−1 packets in sequence. One disadvantage of thismethod is that n-bit signaling outlay results, which is only required ininstances where an SHO situation actually exists. This is the caseduring approximately 30% of the transmission time. In 70% of thetransmission time n−1 bit is in principle unnecessary and simplyincreases the signaling outlay.

Signaling outlay can be saved if an HARQ method is used, in which aquite specific time slot is available in each HARQ channel from a fixedtime. This has the advantage that the HARQ channel number does not haveto be sent specifically and can be determined for example from theso-called system frame number SFN. However, it has the disadvantage ofreduced flexibility with regard to resource allocation, with the resultthat the system as a whole cannot be used optimally and packettransmission is delayed further. As a result, the method as a whole isless efficient.

It would also be possible, when using the SHO method, not to implementsoft-combining and not to superimpose re-transmissions. Since thepackets are not superimposed, it is not necessary to transmit a packetnumber on the physical channel and the signaling for this is notrequired. One disadvantage of this is, however, that the gain due to thesoft-combining method is lost and the data throughput as a whole isreduced.

SUMMARY

The present disclosure addresses the deficiencies noted above in theprior art methods.

An object of the present disclosure is, therefore, to create an improvedmethod for transmitting control data, including a packet number withwhich the control data is transmitted with as much error protection aspossible and at the same time the signaling outlay is reduced as far aspossible. The packet number is source-coded at least together with afurther control parameter for the transmission. In other words, in thesource-coding process the packet number is not simply converted to anumber of predefined information bit (i.e., with a further controlparameter being converted parallel thereto to separate bits and thesebits then being appended to each other) instead the control parametersto be transmitted are first combined in an appropriate manner and thenconverted together to the available bits in the source-coding process.

The source-coding of the packet number together with further controlparameters, e.g., a channel number, transport format, redundancyversion, etc., allows the available code word space to be utilized moreeffectively than if the different control parameters were source-codedseparately and the signaling bits then appended. This is shown veryclearly in the comparison below, in which it is assumed that a specificnumber of bits b is available to code a packet number and a furthercontrol parameter, here for instance a time channel number. The numberMs of packet numbers that can be signaled with a separate coding isM _(s)=2^(b−[log) ² ^(N) ^(T) ^(])  (1)

NT here is the number of time channels used. The number Ms of packetnumbers that can be signaled is thereby the same for all channels.

With common source-coding, however, the mean number Mj of packet numbersthat can be signaled is

$\begin{matrix}{M_{j} = \frac{2^{b}}{N_{T}}} & (2)\end{matrix}$

The following is an example. It is assumed that six time channels wouldsuffice to ensure that a sender can send at any time in a multi-channelstop and wait method. A separate coding for signaling the six channels 3signaling bits would have to be available to code the channel number. Inprinciple, however, it is possible to signal up to eight channels with 3bits. The code word space provided by these 3 signaling bits is,therefore, not fully utilized. Similarly, correspondingly more bitswould have to be available for signaling more than 2 packet numbers; forexample, 2 bits for signaling 4 packet numbers. In other words, a totalof 5 signaling bits has to be transmitted. With common source-coding,however, 6 different channels with 5 different packet numbers perchannel could be signaled within these 5 signaling bits. In other words,there is an additional gain of one packet number, without more signalingbits having to be transmitted.

The method of the invention is particularly advantageous when thetransmission method mentioned above is used. That is to say, withdifferent time channels being available to send the data packets, thechannels being implemented by temporal distribution of the same physicalchannel, and with a data packet being sent repeatedly by thetransmitting device in each instance on one time channel until thetransmitting device receives a confirmation signal from a receivingdevice. In other words, the invention is advantageous in particular witha multi-channel stop and wait ARQ transmission method, in which thepacket numbers for packets to be transmitted for the first time arere-used cyclically. The invention is, however, not restricted to suchtransmission methods but can be used with all methods, in which packetnumbers have to be transmitted with further control parameters forcontrolling the packet-oriented data transmission.

The control parameters, which are source-coded together with the packetnumber, can be a wide range of control parameters. In particular, thechannel number of the time channel, in which the data packet in questionis sent, can be source-coded together with the packet number. Such achannel number of the time channel is transmitted when an asynchronousmethod is used, with which unlike with the so-called partiallysynchronous method the time during which transmission takes place in aspecific time channel is not specifically set.

When transmitting with different time channels on the same physicalchannel (wherein many different time channels are preferably used as amaximum) the sum of the transmission time intervals of the availabletime channels covers the round-trip time; at the end of whichre-transmission can take place on a specific time channel after aprevious transmission. Any larger number of time channels would notimprove system performance. The claimed method restricts the number oftime channels, which is expedient in so far as the unused code space canbe utilized effectively as described above for coding additional packetnumbers. If, for example, transmit time is not permanently available toa sender due to the available resources, it is optionally expedient touse even fewer time channels; such that the round-trip time is notcompletely covered by the sum of the transmission time intervals.

The soft-combining method mentioned above is advantageously used fortransmission, with a number of re-transmissions of a data packet beingsuperimposed by the recipient for decoding a data packet. The individualpacket transmissions can thereby each have specific different and/oridentical elements. If all transmissions have identical bits,soft-combining achieves an increase in energy to facilitate data packetdecoding by the recipient. This method is also referred to aschase-combining.

It is another object of the invention to provide a transmission methodwith so-called incremental redundancy, also referred to hereafter as anIR method. The re-transmissions to some degree have different data, inparticular different redundancy data. By using different redundancy datain the different transmissions of the same packet, it is possible toimprove the code rate as well as achieving an energy increase. The coderate is defined by the ratio of the transmitted useful information bitsto the number of information bits transmitted as a whole. When an IRmethod is used, the recipient must know in each instance whichredundancy bits or which variant the respective transmission contains.To this end, the sender sends the recipient a redundancy versionindicator or redundancy version for short as a further controlparameter. With this method, therefore, the redundancy version indicatoris also preferably source-coded together with the packet number andoptionally also the channel number of the time channel and/or furthercontrol parameters.

Common source-coding means that it is also possible in particular toassign different numbers of packet numbers to the different timechannels to utilize the code space fully. This is shown for example byequation (2), in which the mean number of packet numbers Mj that can besignaled does not necessarily have to result in a whole number. Fullutilization of the code space can be achieved in such instances byassigning some of the channels a higher number of packet numbers thatcan be signaled than others. All distributions P={p1, p2, . . . , pN} ofnumbers of packet numbers pi that can be signaled of the individual timechannels i=1 to N are possible, for which the following applies:

$\begin{matrix}{{\sum\limits_{i = 1}^{N}P_{i}} = {W \leq 2^{b}}} & (3)\end{matrix}$

where pi≧2 and a whole number. W refers to the number of code words usedfrom the maximum 2b options. The code space is utilized to the maximumfor W=2b. In certain conditions, however, a coding can be expedient,with which the code space is not fully utilized, i.e., W<2b, as theunused code words can be used to improve the channel coding performance.As a result, it is possible to achieve a specific target error rate, forexample, with low transmit power for the control channel.

In the above example of five available bits that can be signaled and sixchannel numbers to be signaled, equation (2) gives the mean number ofpacket numbers that can be signaled Mj=5.33. Optimum utilization of thecode space is thereby achieved, in that, for example, six packet numbersthat can be signaled are assigned to two of the time channels and onlyfive packet numbers can be signaled on the further four time channelsrespectively. Similarly different numbers of redundancy versionindicators can also advantageously be assigned to the different timechannels.

These assignments can in principle be completely fixed, i.e. determinedonce before the method. Alternatively however it is also possible forthe number of packet numbers and/or the number of redundancy versions ofat least one of the time channels preferably even all the time channelsto be variable, i.e. to be modified during a data transmission, forexample according to a fixed time rule or by notification of themodified configuration between sender and recipient.

The number of redundancy version indicators of the time channel inquestion can thereby be modified according to a predefined sequence atspecified time intervals. It is particularly preferred for the number ofpacket numbers and optionally also the number of redundancy versionindicators of at least one of the time channels or optionally for allthe time channels, to be selected as a function of the currenttransmission situation. This is particularly advantageous in certainsituations where a larger number of packet numbers may be necessary,while in certain other situations a smaller number of packet numberssuffices. Thus, the number of packet numbers could be increased, forexample, in an SHO situation, while only two packet numbers suffice in anon-SHO situation.

It is another object of the invention to make it possible to switchbetween the different soft-combining methods, with no redundancy versionindicator at all having to be transmitted specifically when theso-called chase-combining method is used. In instances where incrementedredundancy is implemented, however, the number of redundancy versionindicators than can be signaled is increased accordingly. Transmissionresources can be allocated to the senders taking into account the numberof time channels used by the respective devices and/or numbers of packetnumbers and/or numbers of redundancy version indicators of the differenttime channels of the transmitting device in question that can besignaled. In other words, when the data transmission method is used onan uplink, the so-called scheduler, (which can be implemented in thebase station and which allocates transmit times to the differentterminals) knows the distribution functions of the time channels, thenumbers of packet numbers and the numbers of redundancy versionindicators of the individual terminals, and takes these into accountduring resource allocation.

The time channels are also preferably prioritized according to theirnumber of packet numbers when selecting a time channel for a pendingtransmission of a new data packet. In the simplest form, the timechannels that have a higher number of packet numbers can simply bepreferred, which can enhance the overall system performance. In order tobe able to implement this in a simple manner, it is advantageous todistribute a number of packet numbers to the individual time channelssuch that the distribution of the number of packet numbers is amonotonously increasing or monotonously decreasing function in respectof the channel numbers of the available time channels. In other words,as the channel number increases, the respective time channel receivesfewer or more packet numbers that can be signaled. The highest or lowestchannel number of the free time channels in each instance can thenadvantageously be taken into account. This is a particularly simpleselection algorithm that gives preference to time channels with highernumbers of packet numbers during selection. This algorithm can of courseeasily be extended to include the instance where the distribution of thenumber of packet numbers is not monotonous.

In an embodiment of the invention a time channel for a pendingtransmission can also be selected according to a specific selectionrule, taking into account when different combinations of channel numbersand packet numbers were last used. This can be a rule that ispermanently predefined for all senders. One possible rule is, forexample, a simple counting or storing of transmission to date since thelast use of the possible channel number/packet number combination ineach instance. This selection rule can be configured such that thedifferent channel number/packet number combinations are taken intoaccount as well as the numbers of packet numbers on the individual timechannels.

In yet another embodiment of the invention it is also possible for atime channel to be selected taking into account temporal informationrelating to transmission to date on the different time channels. Thistemporal information can for example include the time of the lasttransmission with a specific channel number/packet number combination oreven the mean time period between two successive packet numbers for eachtime channel. In this way it is possible to maximize the time intervalto the recurrence of a specific combination. It is also possible toselect a time channel for a pending transmission of a new data packettaking into account use times of the different time channels to date.The mean use time is preferably taken into account here to minimizeoutlay for the method as far as possible.

The claimed method is particularly advantageous for improving uplinktransmission, In other words, for the transmission of data from themobile radio device to the base station. The mobile radio device musthereby as usual have means for transmitting control parameters on aphysical channel to a base station in the cellular network, in order tocontrol the packet-oriented data transmission from the mobile radiodevice to the base station. As usual, the mobile radio device alsorequires a source-coding device, which source-codes the controlparameters before transmission the control parameters include a packetnumber to identify a data packet. According to the invention, thiscoding device must be configured such that the packet numbers aresource-coded at least together with a further control parameter for thetransmission.

The means for transmitting the control data can include at least onetransmit/receive device with a suitable antenna mechanism and aprocessor device, which controls the different processes within themobile radio device and generates or correspondingly selects the controldata. The source-code device can thereby be implemented in the form ofsoftware within the processor device of the mobile radio device. Thebase station can also have a corresponding decoding device, which isconfigured such that the packet number is decoded together with thefurther control parameters.

It is, however, also possible to use the method for downlink datatransmission. In this instance, the base station must correspondinglyhave means for transmitting the control parameters on the physicalchannel to the mobile radio device and a source-coding device, which isconfigured such that the packet number is source-coded at least togetherwith a further control parameter for the transmission. In this instance,a claimed mobile radio device can have a corresponding decoding device,which is configured such that the packet number is decoded together withthe further control parameters.

BRIEF DESCRIPTION OF THE FIGURES

The various objects, advantages and novel features of the presentdisclosure will be more readily apprehended from the following DetailedDescription when read in conjunction with the enclosed drawings, inwhich:

FIG. 1 illustrates a diagram of the principles of an n-channel stop andwait HARQ method with three different time channels implemented on onephysical channels.

FIG. 2 illustrates a schematic diagram of the coding of controlparameters for a transmission on the physical channel.

FIG. 2 a illustrates a schematic diagram of the source-coding of achannel number of a time channel and a packet number according to theprior art.

FIG. 2 b illustrates a schematic diagram of the source-coding of achannel number of a time channel and a packet number according to anembodiment of the invention.

FIG. 3 illustrates a table, showing the number Ms of packet numbers thatcan be signaled as a function of the number of signaling bits and thetime channels to be signaled with separate coding according to the priorart.

FIG. 4 illustrates a table, showing the mean number of packet numbersthat can be signaled M_(j) as a function of the number of signaling bitsand the time channels to be signaled, with common source-codingaccording to an embodiment of the invention.

FIG. 5 illustrates a table, showing the percentage signaling gain as aresult of common source-coding.

FIG. 6 illustrates a table, showing examples of different distributionfunctions in respect of the numbers of packet numbers that can besignaled in the different time channels.

FIG. 7 illustrates the number of signaling bits available for theindividual control parameters with a total number of six signaling bitsand a separate source-coding according to the prior art.

FIG. 8 illustrates the number of options that can be signaled associatedwith the signaling distribution according to FIG. 7.

FIG. 9 illustrates a diagram of different options that can be signaledwith common source-coding with a total of six signaling bits forcomparison with FIG. 8.

FIG. 10 illustrates a table as in FIG. 9 but for a total of fivesignaling bits.

FIG. 11 illustrates a table as in FIG. 9 but for a total of foursignaling bits.

FIG. 12 illustrates a possible distribution that varies over time of theredundancy versions that can be signaled on different HARQ channels.

FIG. 13 illustrates an exemplary embodiment of a variation over time ofthe number of redundancy version indicators that can be signaled for aspecific time channel.

FIG. 14 illustrates a tabular summary of an exemplary embodiment for amethod for selecting a specific time channel.

DETAILED DESCRIPTION

The invention is described below based on an example asynchronous, fastHARQ method using a multi-channel stop and wait protocol withsoft-combining, as used to transmit data on the HSDPA channel accordingto the most recent UMTS standard. The present invention is particularlysuited for such a method but is in no way limited to this method. It isalso generally assumed—without restricting the invention—that the methodfor transmitting control parameters is used on an uplink channel from amobile radio device to a base station. The term “mobile radio device” inthe sense of this invention refers to all devices with a correspondingmobile function, e.g. a PDA with a mobile radio element.

The principal mode of operation of such an HARQ method is shown inFIG. 1. The upper bar illustrates the temporal situation on the physicalchannel PK used to transmit the data at the sender. The bar belowillustrates the situation with corresponding temporal displacement ofthe transmission time T_(prop) on the physical channel PK at therecipient. The third bar shows the temporal situation on the physicalchannel PK′ used to transmit the return message at the recipient and thelowest bar shows the situation with corresponding temporal displacementof the transmission time T′_(prop) on the physical channel PK′ at thesender.

The data to be transmitted is transmitted in each instance in the formof packets on the physical channel PK. Each packet transmission therebylasts for a precisely specified transmission time interval TTI. Thetransmission time interval TTI on the HSDPA channel is for example 2 ms.

After receiving a transmission, the recipient requires a processing timeTNBP to decode the data and generate a return message (feedbackinformation) for the sender. This feedback information contains apositive confirmation signal ACK (acknowledgement), if it was possibleto decode the data correctly. Otherwise, a negative confirmation signalNACK (not acknowledgement) is feedback. This confirmation signal ACK,NACK has a length T_(ACK) in each instance. On receipt of the feedbackinformation, the sender can use the channel again after a furtherprocessing time T_(UEP) corresponding to the feedback information. Thetime period until the earliest possible re-use of the channel inquestion is referred to as round-trip time T_(RT).

In the event of a positive confirmation signal ACK a new packet can besent on the channel. In the event of a negative confirmation signalNACK, the old one must be re-transmitted. To utilize the transmit timeavailable on the physical channel PK more effectively, said physicalchannel PK is divided into a number of time channels K1, K2, K3hereafter also referred to as HARQ channels without restricting theinvention. In the time interval until the feedback information is sentback and evaluated, the same method can, therefore, be operated on thefurther HARQ channels K1, K2, K3 in time multiplex. Generally, at leastso many HARQ channels K1, K2, K3 are used until it is possible to senddata at any time. In other words, the number of HARQ channels K1, K2, K3is selected such that at least the round-trip time TTI of one timechannel K1, K2, K3 is covered by transmissions on the other timechannels K1, K2, K3.

In the context of this method, “asynchronous” means that are-transmission of a packet can be sent in any transmission timeinterval TTI with the start time t≧K+N_(RT), with k being thetransmission time interval number of the first transmission and N_(RT)the number of transmission time intervals within the round-trip timeT_(rt). Different control parameters are required to control this HARQmethod and these have to be transmitted from the sender to therecipient. The recipient must, therefore, be notified by specificsignaling of both the HARQ channel number KN and whether it is a newpacket or a re-transmission of the last packet. The latter signalingtakes place by means of the packet number PN.

FIG. 2 illustrates a schematic diagram of how the control parameters KN,PN are coded for the transmission. With the methods used to date, e.g.,the HSDPA method in the UMTS standard as described above, a separatesource-coding QC is first carried out of the HARQ channel number KN intothree signaling bits SB and the packet number PN into a further onesignaling bit SB. This is illustrated in more detail in FIG. 2 a. Thesignaling bits SB are then appended to each other and CRC signaling bitsare added. During source-coding so-called CRC (CRC=cyclic redundancycheck) data is also added, which is used by the recipient duringdecoding to verify the correct transmission of the information. Theentire bit sequence is then channel-coded KC, with redundant data, forexample, such as parity bits PB1, PB2 being added to the systematicdata, which resulted during source-coding. In a so-called rate matchingmethod RM, this data is then reduced, such that it can be transmittedwithin a specified transmission time interval TTI of an HARQ channel.

As already described, in many situations it would be more favorable, inparticular for example in the case of a data transmission insoft-handover mode (hereafter referred to as SHO mode) also using thesoft-combining method described above, to use an n-bit packet number PN,where n>1, instead of a 1-bit packet number PN. In such an instance,there is only a risk of confusing a new packet and a re-transmission ofthe last packet, when the recipient in question has been unable todecode any of the transmissions of 2n−1 packets in sequence in themeantime.

The present invention minimizes signaling outlay as far as possibledespite an increase in the number of packet numbers that can besignaled. In other words, to save signaling bits SB, the packet numberPN is source-coded together with other control parameters. In the caseof the exemplary embodiment described below, common source-coding QC ofthe packet number PN takes place together with the HARQ channel number.For example, as illustrated in FIG. 2 b, code word CW is therebyassigned to every combination of a specific packet number PN and aspecific HARQ channel number KN, which is then converted bysource-coding QC to the required number of signaling bits SB. It is,thus, possible to keep the data throughput as high as possible even inSHO mode, while still retaining the advantages of asynchronous HARQ andsoft-combining.

The common source-coding of HARQ channel numbers and packet numbersallows the available code word space to be utilized more effectively.The table in FIG. 3 illustrates the number M_(s) of packet numbers PNthat can be signaled with separate source-coding (according to the priorart) for typical values of numbers N of channel numbers KN that can besignaled and typical numbers b of signaling bits SB. The number M_(s) ofpacket numbers PN that can be signaled was calculated according toequation (1). The number M_(s) of packet numbers PN that can be signaledis thereby the same for all HARQ channels. In comparison, the table inFIG. 4 illustrates the mean number M_(j) of packet numbers PN that canbe signaled calculated correspondingly according to equation (2) withcommon source-coding according to the present invention. The table inFIG. 5 illustrates the corresponding percentage gain due to commoncoding.

A total of 4 signaling bits SB are available on the HSDPA channelmentioned above for signaling the channel number KN and the packetnumber PN, with 3 bits being reserved for the channel number. As withn-bit coding precisely 2n channels can be signaled, it is possible tosignal 8 channels with these 3 signaling bits. As on the other hand theround-trip time TRT is only 6 transmission time intervals TTI, 6channels would suffice for a sender to be able to send at any time. Thetwo additional possible channels are not needed per se. As shown in thetable in FIG. 3, however, with a separate source-coding only two packetnumbers can be signaled with a total of b=4 signaling bits, irrespectiveof whether 6 or 8 HARQ channels are signaled. In contrast, the table inFIG. 4 illustrates that with a common coding a mean total of 2.67 packetnumbers can advantageously be signaled with 4 bits and 6 HARQ channels.In other words, 3 packet numbers can be signaled for ⅔ (i.e. 4) of theHARQ channels and 2 packet numbers can be signaled for ⅓ (i.e. 2) of theHARQ channels. This corresponds to a gain of 33%. This exampleillustrates very clearly how the number of HARQ channels can expedientlybe reduced to the minimum number predefined by the round-trip time TRTwith the aid of the claimed method and the code space released as aresult can be used for signaling the packet number.

If, however, the sender cannot transmit permanently due to limitedresources, it can be expedient to reduce the number of HARQ channels tobelow the minimum number predefined by the round-trip time T_(RT),thereby achieving even more signaling gain for the packet number, whichfurther reduces the probability of error due to packet confusion.

As the example above shows, the claimed method makes it possible andoften also expedient to use a different number of packet numbers PN thatcan be signaled quite specifically for different HARQ channels. In otherwords, the total number of code words can be allocated in a flexiblemanner to the individual HARQ channels. All the distributions P={p₁, p₂,. . . , p_(N)} of the number of packet numbers p_(i) that can besignaled as described above with reference to equation (3) are therebyalways possible.

A further possibility for optimization results from the fact that thenumber of HARQ channels used and/or the distribution function P of thenumber of packet numbers that can be signaled changes over time. Theseparameters can, for example, very, depending on whether or not theterminal in question is in SHO mode or whether or not the IR method(method with incremental redundancy) described above is used. Otherconnection and network characteristics, such as cell utilization, canalso be taken into consideration.

If network utilization is low, a relatively homogenous distribution isadvantageous, for example, as a terminal wishing to transmit is thenvery likely to be able to transmit in a number of successivetransmission time intervals TTI and all the HAR channels are thereforein use. If network utilization is high, a specific terminal will rarelybe assigned resources in a continuous manner within the round-trip timeT_(RT), so that only a few HARQ channels are generally in use. It isthen advantageous to assign a higher number of packet numbers that canbe signaled to these HARQ channels, in particular in SHO mode. Thechannels with a higher number of packet numbers that can be signaled canthereby preferably be used, in particular in SHO mode, thus reducing theprobability of error due to lost packets. Notification of currentconfigurations can thereby also be sent (e.g., semi-statically) from thenetwork to the terminals. In particular, the base station schedulerknows the distribution function P of the terminals and can take thisinto account when deciding on resource allocation.

Different exemplary embodiments of possible packet number distributionsP={p₁, p₂, . . . , p_(N)} in the different HARQ channels are describedbelow with reference to the table in FIG. 6. The table illustrates asummary of different distributions P as a function of the number ofinformation bits and HARQ channels. It should be noted that allpermutations of a distribution P are in principle equivalent, as long asthe selection algorithm of the HARQ channels is tailored to this. Itshould also be noted that the variants shown in FIG. 6 are only aselection of all possible variants.

A round-trip time of six transmission time intervals TTI is assumed inall the exemplary embodiments according to FIG. 6. It is also assumedthat the only soft-combining method used is a chase-combining method,i.e., no incremental redundancy is used, or that the source-coding ofthe redundancy version is independent thereof. With common source-codingthe number of HARQ channels N used can first be reduced from eight tosix, without loss of performance, even with low network utilization. Thecode words can also be distributed in a flexible manner to these 6channels.

The proposed distribution functions can thereby be classified in threegroups:

-   -   Type 1: identical distribution functions. All the numbers of        packet numbers pi in the different HARQ channels i are thereby        identical.    -   Type 2: homogenous distribution functions. Subject to the basic        condition of full code space utilization W=2b, the numbers of        packet numbers pi are selected such that the difference between        the maximum and minimum numbers of packet numbers pi is minimal        in the different HARQ channels i, i.e., they differ by 1        maximum.    -   Type 3: inhomogenous distribution functions. These are all other        distribution functions.

The different types are specified in the first column of the table.

In the exemplary embodiments in the first line of the table, a total ofb=4 signaling bits are available for signaling the 6 HARQ channels andthe packet numbers. These are typical values for transmission timeintervals TTI of 2 ms, as used with HSDPA, and as may also be used in animproved, faster uplink channel, e.g., the EDCH (enhanced dedicatedchannel).

A number of variants are also possible:

1. Constantly Identical Source-Coding:

With this variant it is advantageous to use a distribution P of thenumber of packet numbers that can be signaled on the six HARQ channels,as optimized for the instances mainly occurring. As SHO mode only occursaround 30% of the time, it appears to be expedient not to use more than4 information bits (as in HSDPA). However, to reduce the probability oferror for some HARQ channels in SHO mode, a homogenous or inhomogenousdistribution (types A2 and A3) should be used, e.g., {3, 3, 3, 3, 2, 2},{4, 3, 3, 2, 2, 2}, {4, 4, 2, 2, 2, 2} or {5, 3, 2, 2, 2, 2}. Thefigures {p₁, p₂, . . . , p_(N)} in the brackets hereby referrespectively to the number of packet numbers pi that can be signaled forthe HARQ channel i. The precise choice of distribution is a function ofthe frequency of error as a function of the number of packet numbersthat can be signaled and the assumed utilization of the system. Thehigher the mean assumed utilization of the system (i.e., the cells), thefewer HARQ channels have to have a high number of packet numbers thatcan be signaled.

Alternatively, 5 information bits (types B1, B2 and B3) can be used.There are then 32 signaling options and according to the considerationsabove it is advantageous to use the distributions {8, 8, 8, 3, 3, 2},{8, 8, 8, 4, 2, 2}, {6, 6, 6, 6, 4, 4}, {7, 7, 7, 7, 2, 2}, {6, 6, 5, 5,5, 5} for example. It should be noted that here 5 information bitssuffice to establish a similar basic error protection in the majority ofcases occurring as with 6 information bits with separate source-coding(namely 8 packet numbers that can be signaled). By saving informationbits, it is now possible to use a lower code rate with the same numberof coded bits and achieve a coding gain. This again increases theprobability that the recipients will be able to decode the informationcorrectly. If a code rate of 0.5 is assumed for 6 information bits, thecode rate is 0.42 for 5 information bits and 0.33 for 4 informationbits.

2. Different Source-Coding Depending on SHO Mode But Constant Number ofInformation Bits:

With this variant for example 4 information bits are always used. Thedistribution function varies depending on whether or not SHO mode ispresent. In the non-SHO instance as homogenous a distribution aspossible, such as {3, 3, 3, 3, 2, 2} can be used. An identicaldistribution {2, 2, 2, 2, 2, 2} is also possible. This leaves unusedcode words, which can be used to make a code word selection thatoptimizes the channel coding performance.

In contrast in SHO mode an inhomogenous distribution can be used, suchas {4, 3, 3, 2, 2, 2}, {4, 4, 2, 2, 2, 2} or {5, 3, 2, 2, 2, 2} or {6,2, 2, 2, 2, 2}. To increase the number of packet numbers that can besignaled, it is also possible to reduce the number of HARQ channels. Iffor example only 5 channels are configured, options result such as {5,4, 3, 2, 2}, {5, 5, 2, 2, 2}, {6, 4, 2, 2, 2}, {6, 3, 3, 2, 2}.

It should be noted that reducing the number of HARQ channels to belowthe minimum number required for the round-trip can mean that a specificterminal is unable to transmit at many times. Once there are a number ofterminals in a cell, it is, however, unlikely that no single terminalwould be able to transmit at a specific time. Also the base stationscheduler can take this circumstance into account when allocatingresources. The gain due to the reduction in the probability of error dueto packet confusion can then more than compensate for the loss (ofmulti-user diversity) due to the reduction in the HARQ channels. Ageneral advantage of this variant is that the constant number ofinformation bits means that the same channel coding can always be used.

3. Different Source-Coding Depending on SHO Mode with a Variable Numberof Information Bits:

This variant loses the advantage of variant 2 in favor of more flexibleadaptation. For example, in the non-SHO instance 4 information bits canbe used and a distribution can be employed as described in the tableunder type A1 or A2. In contrast in SHO mode 5 information bits can beused, as a result of which higher numbers of packet numbers that can besignaled can be achieved. Examples of these are found in the table undertypes B1, B2, B3. If, however, the same channel coding (as in variant 2)is used, this can be done by saving bits in other areas of the controlinformation.

For example in SHO mode fewer parameters may suffice for signaling aredundancy version. A distinction between self-decodable andnon-self-decodable packets (as proposed in the current HARQ method forHSDPA) may then be superfluous. This is because it can often happen inSHO mode that a base station does not receive the first packet. If thesecond packet sent is then a non-self-decodable packet, the base stationwill be unable to decode this packet alone. In this instance, theparameter for the so-called redundancy version can be omitted too andthe redundancy version is then calculated by a predefined algorithm fromthe frame number or similar numbering. This is because it can oftenhappen in SHO mode that a base station can only receive some of thepackets, while the others are received by another base station instead.As the mobile station does not know precisely which base stationreceives which packets, it cannot optimize the sequence of theredundancy versions as well as the base station, for example, with atransmission on the HSDPA downlink channel. Alternatively, the parameterfor the redundancy version can be reduced to fewer bits, e.g., just 1bit in SHO mode but 3 bits without SHO. Redundancy version signaling isalso not required if only chase-combining is used, as here alltransmissions of a packet are implemented with identical bits.

4. Different Source-Coding by Means of Specific Signaling by theNetwork:

This variant offers even greater flexibility in that the networknotifies the terminals dynamically of the HARQ configuration (i.e., thenumber of HARQ channels and the number of packet numbers that can besignaled for each channel) to be used. This can also be linked to anautomatic modification of the HARQ configuration depending on the SHOmode. This has the advantage that no specific signaling is required. Theadditional flexibility also allows the network to adapt the distributionfunction to network utilization.

The following distributions can be used here by way of an example:

non-SHO mode: {3, 3, 3, 3, 2, 2}

SHO mode, low network utilization: {4, 3, 3, 2, 2, 2}

SHO mode, mean network utilization: {5, 3, 2, 2, 2, 2}

SHO mode, high network utilization: {6, 4, 2, 2, 2}

Only 4 information bits are always used with this variant.

It is, however, also possible to increase the number of information bitsin SHO, e.g.:

non-SHO mode: {3, 3, 3, 3, 2, 2}

SHO mode, low network utilization: {6, 6, 5, 5, 5, 5}

SHO mode, mean network utilization: {7, 7, 7, 7, 2, 2}

SHO mode, high network utilization: {8, 8, 8, 4, 2, 2}

Code space utilization efficiency can also be increased by includingfurther control parameters that have to be sent with every packet in thecommon source-coding. These include the control parameters, for example,that describe the transport format used. If an IR method is used, therecipient also needs the redundancy version, which contains informationabout the coded bits in the respective transmission. With such a method,therefore, the packet number and optionally also the HARQ channel numberare preferably source-coded together with the redundancy version. Adifferent number of redundancy versions that can be signaled can therebypreferably be used for different HARQ channels. The distributionfunction Q of the number of redundancy versions a_(i) that can besignaled for each HARQ channel i can also be adapted and optimizedtaking into account connection and network characteristics (SHO mode ornon-SHO mode, cell utilization).

In non-SHO mode, the probability that a recipient can detect andsuperimpose a number of successive transmissions of a packet is veryhigh. It, therefore, makes sense to use incremental redundancy in thismode, to achieve an additional decoding gain by lowering the code rateby re-transmitting packets. In SHO mode, however, this probability islower, so the additional gain due to incremental redundancy issignificantly reduced or can even become disadvantageous in the case ofso-called “full IR”, where not all transmissions can be decoded aloneper se. It is, therefore, expedient in SHO mode just to use achase-combining method or the so-called partial IR method, where alltransmissions can be decoded alone per se (self-decodable). In thisinstance, a signaling whether or not the message is a self-decodablemessage is not necessary. If just a chase-combining method is used inSHO mode, these bits can be used for signaling packet numbers.

The table in FIG. 7 illustrates the distribution of signaling bits, whena total of b=6 signaling bits is used with a separate source-coding ofthe parameters according to the prior art. The associated number ofoptions that can be signaled is shown in the table in FIG. 8. If thethree parameters packet number PN, HARQ channel KN and redundancyversion RV—are source-coded together according to the claimed method,the following further optimization is for example then possible:

In the non-SHO instance only 2 packet numbers are required, so the othersignaling options can be distributed to the possible redundancyversions. In this instance, the mean number Lj, non-SHO of redundancyversions that can be signaled is obtained using the following equation:

$\begin{matrix}{L_{j,{{non} - {SHO}}} = \frac{2^{b}}{2N_{HARQ}}} & (4)\end{matrix}$

If N=6 channels is assumed, as in the above exemplary embodiments, and atotal of b=6 signaling bits is used, the mean number of redundancyversions that can be signaled rises to 5.33. If a chase-combining methodis used in SHO mode, signaling of the redundancy version is notnecessary. The mean number of packet numbers that can be signaled istherefore obtained using equation (2) as before. In the examplementioned, a mean number of 10.67 packet numbers that can be signaled isachieved.

The table in FIG. 9 summarizes these exemplary embodiments in the firsttwo lines. The type of possible distribution functions according to thetable in FIG. 6 is given in brackets in each instance. However,generally, a really large number of redundancy versions that can besignaled is not necessary. The required number of packet numbers PN thatcan be signaled can also be less than 8 in some instances, as can bedetermined by error probability simulations. It can, therefore, also beexpedient to save a bit by such common source-coding. In other words,only using b=5 signaling bits instead of b=6 signaling bits. A meannumber of 2.67 redundancy versions that can be signaled is then possiblefor each HARQ channel according to the above procedure in the non-SHOinstance.

In SHO mode signaling of the redundancy version is again not necessary.This means that a mean number of 5.33 packet numbers that can besignaled is implemented with 5 bits. This particularly preferredembodiment is summarized again in the table in FIG. 10. The table inFIG. 11 shows the corresponding values for b=4. With commonsource-coding of the redundancy version as well the above statementapplies by analogy that in non-SHO mode it is possible to assign alarger number of redundancy versions that can be signaled quitespecifically to specific HARQ channels and these can then also be usedin preference. All further statements relating to the distributionfunction P of the number of packet numbers that can be signaledtherefore also apply by analogy for a distribution function Q of thenumber of redundancy versions that can be signaled.

As a further option this method can also be used in a scenario whereincremental redundancy is also used in SHO mode. If the mean number ofredundancy versions that can be signaled is Lj,SHO, the mean number ofpacket numbers that can be signaled in SHO Mj,SHO is calculatedaccording to the equation:

$\begin{matrix}{M_{j.{SHO}} = \frac{2^{b}}{L_{j,{SHO}} \cdot H_{HARQ}}} & (5)\end{matrix}$

The third line of the table in FIG. 9 shows such an example for b=6. Itis also possible to modify the equation (5) for a specific required meannumber Mj of packet numbers that can be signaled and required HARQchannels to determine the mean number of redundancy versions that can besignaled. The fourth line in the table in FIG. 9 shows this for b=6 anda mean number Mj=8 packet numbers that can be signaled.

With IR methods there is an additional optimization option of using adistribution function Q that changes over time for the number ofredundancy versions that can be signaled a_(i) for each HARQ channel i,with the object of optimizing the number of redundancy versions that canbe used during packet transmissions. When using type I from the table inFIG. 6 (b=3) on average 1.33 redundancy versions can be signaled. Thismeans that two redundancy versions can be signaled for two HARQ channelsand just one redundancy version for the other four HARQ channels. Thismeans that the performance for these four HARQ channels is not as goodas for the first two. This fact can be taken into account when selectingthe channels, in that the two HARQ channels, on which two redundancyversions can be signaled, are used in preference. However, with a fulldata throughput it is necessary to use all the HARQ channels. In orderto achieve a good performance for all channels in this instance, thenumber of redundancy versions that can be signaled can preferably beassigned to the channels in a manner that changes over time. At one timethen two redundancy versions could be signaled for the first twochannels but at a later time they could be signaled for other channels.

FIG. 12 illustrates a possible use situation. The lines of the tablerepresent arbitrary, preferably fixed time units. The time units arethereby selected such that they correspond to the round-trip time TRTfor the HARQ process. During time unit 1 the higher number of redundancyversions (in this instance two redundancy versions) can be signaled forchannels 1 and 2, during time unit 2 for channels 3 and 4 and duringtime unit 3 for channels 5 and 6. The preferred channels, therefore,change. At the end of time unit 3, the pattern can be repeated or adifferent pattern can be used, as illustrated in the table. Thesepatterns can then be repeated or combined in any manner. Variableassignment over time allows the different channels to achieve the sameperformance. In particular, it means that more than just one redundancyversion can be signaled for all channels.

The following principles apply when selecting redundancy versions:

A different redundancy version from the one used during the firsttransmission should be used for a re-transmission. Therefore if tworedundancy versions can be signaled during the re-transmission, the onethat was not used during the first transmission should be signaled. Iftwo redundancy versions can be transmitted during the firsttransmission, the selection should be made in a forward-looking manner,such that a different redundancy version can be signaled for there-transmission. If at the anticipated time of the (potentiallynecessary) re-transmission only one redundancy version can be signaled,a different redundancy version should be selected during a firsttransmission with a view to the future. If more than one HARQ channelcan be selected at a certain time, said selection can also take intoaccount whether a favorable redundancy version can be signaled on thechannel.

If the data is transmitted at maximum utilization, all the HARQ channelsare active. If 1.5 redundancy versions are available for each HARQchannel, it can be ensured with the forward-looking allocation describedthat different redundancy versions can always be signaled duringre-transmissions. However, in the above example only 1.33 redundancyversions are available, but an optimum strategy can be designed for thistoo.

FIG. 13 illustrates the redundancy versions that can be signaled foreach time unit. Only one HARQ channel is shown for clarity. With thedescribed assignment a different redundancy version from the onesignaled for the first packet can always be signaled for there-transmitted packet, if both packets are sent at successive times.This is also true, if the re-transmitted packet is sent in the next butone time interval. Only if the packet is re-transmitted after three timeintervals, is this not possible in ⅔ of cases. With such long timeintervals however, there are generally a number of HARQ channels, sothat a suitable channel can be selected as described above.

As already mentioned above, the channels can preferably be used with ahigher number of packet numbers that can be signaled in particular inSHO mode—thereby reducing the probability of error due to lost packets.In order to achieve a correspondence between the distribution function Pthat is predefined or signaled by the network and the HARQ channelsactually used by the terminal, the sequence must be specified, in whichthe HARQ channels are to be used. Such an algorithm must be prescribedfor all senders. The selection algorithm should be tailored to thedistribution function.

In a particularly simple instance the distribution function P is amonotonously decreasing (or increasing) function in respect of the HARQchannel number, i.e. p_(i)≦p_(j) (or p_(i)≧p_(j)) for all i>j. Thisallows the use of a very fast, uncomplicated selection algorithm, withwhich the smallest possible (or largest possible) free channel number issimply used in each instance. This ensures that the channels with ahigher number of packets numbers that can be signaled are actually usedin preference. This algorithm is based on the concept that on averagethe HARQ channel with the highest number of packet numbers that can besignaled will also have the highest number of completed transmissionsuntil the same packet number is re-used. On average this also reducesthe probability of incorrect superimposition of two transmissions.

A further, higher-performance algorithm involves maximizing the timeperiod between the repetition of a specific combination of HARQ channelnumber and packet number. This can be achieved by storing the time oflast use for every HARQ channel/packet number combination and alwaysselecting the free combination with the oldest entry. If a number ofentries are of the same age, further criteria can optionally be used. Inthis instance it may for example be expedient to prefer a combinationwith a slightly more recent date, if it has a higher number of packetnumbers that can be signaled. The reason for this is that the pattern ofachievable time intervals may be more favorable in the future.

Alternatively the number of transmissions last carried out can also bestored for every HARQ channel/packet number combination. For everypacket to be transmitted for the first time, the free HARQ channel forwhich the maximum number of transmissions has been carried out since thelast use of the current packet number is selected. See FIG. 14 furtherillustrates the details of this selection method. It is thereby assumedthat 6 channels are currently free. The number of packets numbers thatcan be signaled in the different channels is P={4, 3, 3, 2, 2, 2}, asshown in the 2nd column of the table. The corresponding fields aremarked with a dash for channels that can signal fewer than 4 packetnumbers. The generally available packet numbers are constantly used in acyclically alternating manner for each HARQ channel i. For example thecurrent packet number _(pa,i)—i.e., the packet number to be used for thenext first transmission—can be calculated by increasing the last usedpacket number of this HARQ channel and the modulo operation:p _(a,i)=(p _(a-1,i)+1)mod p _(i)  (6)

In the example illustrated in FIG. 14, the values according to column 3of the table, which are shaded in the table, are used as the currentpacket numbers. The number of transmissions since the last use of thecurrent packet number to be used in each instance can be calculated foreach of the HARQ channels by adding together all the transmissions n(p)with packet numbers that are not the same as the current one:

$\begin{matrix}{N_{i} = {\sum\limits_{\underset{k \neq n_{i}}{k = 1}}^{p_{i}}n_{k,i}}} & (7)\end{matrix}$

The free channel having the maximum Ni can be selected. In the exampledescribed above, this is the HARQ channel 3.

This example illustrates that the free HARQ channel with the highestnumber of packet numbers that can be signaled does not necessarilyalways have to be preferred. The second algorithm shown is, therefore,more complex but is higher-performance than the first, simple algorithm.The second algorithm ensures that the HARQ channel, in which the highestpossible number of transmissions have been carried out since the lastuse of the current packet number, is used. Packets can, therefore, onlybe confused, if a recipient has been unable to decode precisely thisnumber of transmissions of the control information to this HARQ channel.One disadvantage is that the number of transmissions n_(k,i) must bestored for every HARQ channel/packet number combination.

It is possible to reduce the storage requirement of the secondalgorithm, if only the mean number of transmissions for each packetnumber n_(i) is stored for each HARQ channel. The number N_(i) oftransmissions since the last use is then calculated as follows:N _(i)=(p _(i)−1)· n _(i)   (8)with

$\begin{matrix}{{\overset{\_}{n}\;}_{i} = {\frac{1}{1}{\sum\limits_{k = 1}^{1}n_{k,i}}}} & (9)\end{matrix}$

with the last 1≦p_(i) values being used for averaging in each instance.The storage requirement is then a function of the number of supportpoints 1 that are used for averaging and is N.1 where N is the number ofHARQ channels again. If only one value is used for each HARQ channel(l=1) in the above example the storage outlay drops from 16 values to 6values, even to 12 values for l=2. The reliability of the mean valueincreases as the number of support points l increases. For l=pi thissimplified algorithm is identical to the one described above.

The algorithm is further improved if in addition to the number oftransmissions for each HARQ channel, the time that has elapsed is alsotaken into account. If this time is very short and for example withinthe so-called coherence time of the mobile radio channel, within whichthe channel characteristics are approximately constant, it is possiblethat it will not be possible for even a large number of transmissions tobe decoded by a specific recipient. This is the case for example whensaid radio transmission takes place in a fade situation, in which thereceive level is very low and/or if the sender is already transmittingat the maximum possible transmit power. The probability that all theinterim transmissions on an HARQ channel will be lost thereforedecreases as the elapsed time increases (so-called temporal diversity).

With an improved algorithm therefore an associated time informationelement is stored in addition to the number of transmissions of eachHARQ channel/packet number combination, for example the time of the lasttransmission of an HARQ channel/packet number combination or the meantime period between two successive packet numbers for every HARQchannel. The method operates in the same way as the algorithms outlinedabove but with the parameter “time of last transmission” stored insteadof the parameter “number of transmissions” or the “mean time periodbetween two successive packet numbers” instead of the “mean number oftransmissions for each packet number”. The HARQ channel for the nextpending packet is then selected taking into account both the criteria ofnumber of transmissions since the last use and the time that has therebyelapsed. This can be done for example by means of a weighted summationof the two criteria or a multiplication.

In principle it is also possible for the selection algorithm for theHARQ channel also to be based solely on the criterion “time period ofthe last transmission of an HARQ channel/packet number combination”. Afurther algorithm based on the mean use time of each HARQ channel isdescribed below:

At the start the use times for all channels are initiated at an initialvalue, with the initial value also being able to be different fordifferent HARQ channels. In particular the initial value for the HARQchannels having a large number of packet numbers can be selected greaterthan for the HARQ channels with a smaller number of packet numbers.Whenever a new packet is sent, the following steps are carried out:

The use times for all HARQ channels are increased by a uniform valueirrespective of the number of channel numbers of the channels. Howeverthe use time for those channels that already have a very high use timecan be increased less or the use time is limited to a maximum value.This maximum value can also be different for different HARQ channels. Inparticular the maximum value for HARQ channels having a large number ofpacket numbers can be selected greater than for channels with a smallernumber of packet numbers.

The channel with the longest use time is then selected and the nextpacket is sent via this channel. However only the channels which arefree to send a new packet are considered, in other words those where thesender is not still awaiting an outstanding confirmation. The use timefor the selected channel is then reduced, with this reduction being ableto be different for different HARQ channels. In particular the reductionfor HARQ channels again having a large number of packet numbers can beselected smaller than for HARQ channels with a smaller number of packetnumbers.

Instead of a maximum value limit, it can also be specified that if themaximum value is exceeded, the use time is reduced by an amount that isproportional to the amount by which the maximum value is exceeded. Inthe simplest instance this can be implemented, when the proportionalityfactor is a power of two, e.g. ¼. The examples show how the claimedmethod can be used to minimize the probability of error due tomisinterpretation of packet numbers due to lost packets withoutadditional signaling outlay. Only one common source-coding specificationis thereby required for every combination used of numbers of HARQchannels used and/or distribution functions P of the number of packetnumbers that can be signaled and/or distribution functions Q of thenumber of redundancy versions that can be signaled and this is known toboth sender and recipient.

Finally it should be noted that the transmission methods shownspecifically in the figures and described above are only exemplaryembodiments, which can be modified by the person skilled in the art,without departing from the scope of the invention. Therefore, only theredundancy version and optionally also further other control parameterscould be source-coded together with the packet number, for example whenit is not necessary to transmit the number of the HARQ channel whenusing a partially synchronous HARQ method.

While the invention has been described with reference to one or moreexemplary embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiments disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

LIST OF REFERENCE CHARACTERS

B Number of signaling bits N Number of channel numbers Ms Number ofpacket numbers Mj Mean number of packet numbers QC Source-coding KCChannel coding RM Rate-matching method CW Code word PN Packet number KNTime channel number RV Redundancy version indicator K1 Time channel K2Time channel K3 Time channel PK Physical channel PK′ Physical channel SBSignaling bit CRC CRC check bit PB1 Parity bit PB2 Parity bit TTITransmission time interval ACK Positive confirmation signal NACKNegative confirmation signal TRT Round-trip time TACK Signal length TNBPProcessing time TUEP Processing time Tprop Transmission time T′propTransmission time

1. A method for transmitting control parameters on a physical channelbetween a mobile radio device and a base station in a cellular network,comprising: providing with the control parameters a packet number foridentifying a data packet; source coding, via a source coding device,the packet number together with at least one further of the controlparameters for the transmission, wherein the control parameters are usedfor controlling a packet-oriented data transmission between the mobileradio device and the base station; transmitting, via a transmissiondevice, the at least one further of the control parameters and thepacket number between the mobile radio device and the base station;implementing by a temporal distribution of the same physical channel, aplurality of different time channels available for sending data packets;re-transmitting a data packet on one of the plurality of different timechannels using the transmitting device in each instance, until thetransmitting device receives a confirmation signal from a receivingdevice; and using at most so many different ones of the plurality ofdifferent time channels such that a sum of transmission time intervalsof the different ones of the plurality of different time channels coversa round-trip time span at the end of which a re-transmission after aprevious transmission can take place at the earliest on a specific oneof the plurality of different time channels.
 2. The method according toclaim 1, further comprising including with the at least one further ofthe control parameters a channel number of the one of the plurality ofdifferent time channels, in which the data packet in question is sent.3. The method according to claim 1, wherein a number of re-transmissionsof the data packet are superimposed to decode the data packet.
 4. Themethod according to claim 3, wherein an incremental redundancy method isused during the data packet transmission and the at least one further ofthe control parameters includes a redundancy version indicator.
 5. Themethod according to claim 1, wherein the data packet transmission takesplace by means of a multi-channel HARQ transmission method and the atleast one further of the control parameters includes an HARQ parameter.6. The method according to claim 1, wherein different numbers of packetnumbers are assigned to different time channels, which are available foridentifying the data packet on the time channel in question.
 7. A methodfor transmitting control parameters on a physical channel between amobile radio device and a base station in a cellular network,comprising: providing with the control parameters a packet number foridentifying a data packet; source coding, via a source coding device,the packet number together with at least one further of the controlparameters for the transmission, wherein the control parameters are usedfor controlling a packet-oriented data transmission between the mobileradio device and the base station; transmitting, via a transmissiondevice, the at least one further of the control parameters and thepacket number between the mobile radio device and the base station;implementing by a temporal distribution of the same physical channel, aplurality of different time channels available for sending data packets;and re-transmitting a data packet on one of the plurality of differenttime channels using the transmitting device in each instance, until thetransmitting device receives a confirmation signal from a receivingdevice; wherein a number of re-transmissions of the data packet aresuperimposed to decode the data packet; wherein an incrementalredundancy method is used during the data packet transmission and the atleast one further of the control parameters includes a redundancyversion indicator; wherein different numbers of redundancy versionindicators are assigned to different time channels of the plurality ofdifferent time channels, which are available for signaling theredundancy version of the data packet transmission on said one of theplurality of different time channel.
 8. The method according to claim 7,wherein at least one of a number of packet numbers and a number ofredundancy version indicators of at least one of the plurality ofdifferent time channels are varied.
 9. The method according to claim 8,wherein the number of redundancy version indicators of the time channelin question is modified according to a predefined sequence at specifictime intervals.
 10. The method according to claim 7, wherein at leastone of a number of packet numbers and a number of redundancy versionindicators of at least one of the plurality of different time channelsare selected in each instance as a function of the current transmissionsituation.
 11. The method according to claim 7, wherein transmissionresources are allocated to a specific transmitting device taking intoaccount at least one of a number of said different time channels used bythe device in question, a number of packet numbers, and a number of theredundancy version indicators of the different time channels of thespecific transmitting device in question.
 12. A method for transmittingcontrol parameters on a physical channel between a mobile radio deviceand a base station in a cellular network, comprising: providing with thecontrol parameters a packet number for identifying a data packet; sourcecoding, via a source coding device, the packet number together with atleast one further of the control parameters for the transmission,wherein the control parameters are used for controlling apacket-oriented data transmission between the mobile radio device andthe base station; transmitting, via a transmission device, the at leastone further of the control parameters and the packet number between themobile radio device and the base station; implementing by a temporaldistribution of the same physical channel, a plurality of different timechannels available for sending data packets; and re-transmitting a datapacket on one of the plurality of different time channels using thetransmitting device in each instance, until the transmitting devicereceives a confirmation signal from a receiving device; whereindifferent numbers of packet numbers are assigned to said different timechannels, which are available for identifying the data packet on thetime channel in question; wherein during selection of the one of theplurality of different time channels for a pending transmission of thedata packet, the plurality of different time channels are prioritizedaccording to their numbers of packet numbers.
 13. The method accordingto claim 12, wherein a packet number distribution function, whichdefines a number of packet numbers assigned to individual time channelsin the plurality of different time channels, is a monotonouslyincreasing or monotonously decreasing function with respect to channelnumbers of available time channels.
 14. The method according to claim12, wherein one of the plurality of time channels is selected for thepending transmission of the data packet according to a specificselection rule, taking into account when different combinations ofchannel numbers and packet numbers were last used.
 15. The methodaccording to claim 12, wherein a time channel is selected for thepending transmission of the data packet taking into account temporalinformation relating to transmissions to date on the different timechannels of the plurality of different time channels.
 16. The methodaccording to claim 15, wherein one of the plurality of different timechannels is selected for the pending transmission of the data packettaking into account use times to date of the different time channels ofthe plurality of different time channels.